Instruments for use in performing gel injection adjustable keratoplasty

ABSTRACT

The present invention provides a surgical technique and instrument kit that allows for subtle modification of the corneal curvature by interlamellar injection of a synthetic gel at the corneal periphery while sparing the optical zone. The gel viscosity, volume and disposition within the surgical annular track as well as the diameter of the track, width, depth, and location are all parameters in the refractive change obtained. Following ultrasonic pachymetry performed centrally and at a selected wound entrance located about 2.5 to 3.5 mm from the apex, a one millimeter or so wide, about 75-85% corneal thickness depth radial incision is performed with a micrometric diamond knife adjusted to about 86% corneal thickness. Inserted through the partial-depth incision, a corkscrew-like dissector or helicoidal spatula forms a 360° annular track centered about the apex. A transparent gel is manually injected through the incision, filling the annular channel. Using a surgical keratometer mounted to an operation microscope, the final corneal power is adjusted by massaging and removing the gel as necessary during the primary procedure or subsequent procedures, as the GIAK technique is reversible.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. Ser. No. 07/836,711,filed Feb. 19, 1992, now U.S. Pat. No. 5,372,580 which was acontinuation-in-part of U.S. Ser. No. 07/551,807, filed Jul. 12, 1990,which is now U.S. Pat. No. 5,090,955.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a technique for intra-operativecorrection of refractive error to eliminate the need for eyeglasses andcontact lenses. More particularly, the invention relates to a techniquefor surgically correcting myopia and astigmatism by controlledinterlamellar annular injection of a polymeric gel at the cornealperiphery so as to modify the corneal curvature, while sparing thecentral optical zone.

2. Description of the Related Art

The ideal surgical procedure in refractive surgery could be defined asone which allows all the advantages of eyeglasses or contact lenses,that is, one which offers effectiveness or a wide range of corrections,allowing correction of ametropias both large and small; accuracy orpredictability, allowing for correction of a certain amount of ametropiawith precision; alterability or reversibility, so that if ocularrefractive changes occur might be possible to adjust the correctionagain; innocuousness or without complications, that is, the proceduredoes not lead to adverse situations; visual quality without alterationsin the size of the image or of the visual field; technical simplicity,that is, not requiring sophisticated techniques to be put into practice;availability; low cost; and aesthetically acceptable on the part of thepatient.

A number of surgical techniques have been proposed which have the objectof intra-operative correction of refractive error. Examples are RadialKeratotomy, Keratomileusis, Epikeratoplasty, and Excimer LaserReprofiling of the Corneal Surface also known as Photo RefractiveKeratoplasty (PRK). These methods work with the characteristics of thecornea in order to modify either its curvature or its refractive index.Perhaps the more widespread method and the one which best approaches theobjects noted above is radial keratotomy, basically because it can beperformed at low cost without the need for additional materials. Howeverthis procedure has a number of limitations, including the presence ofadverse situations (glare) and a lack of stability, predictability(hypercorrection or hypocorrection) and reversibility. The remainingprocedures described and presently in use demand very sophisticatedsurgical equipment requiring very specialized training and also the useof synthetic or natural materials that reduce the likelihood of theprocedure being available in the average clinic. Further, with thepresent surgical techniques it is not possible to accurately predict thepatient's refractive outcome, due in part to corneal hydration andsubsequent wound healing processes.

Yet a further prior procedure made use of a rubber annular implant(intrastromal rings) which were surgically inserted to alter cornealcurvature. However, that procedure, which was introduced in 1986 by theinventor of the subject procedure, involved stromal delamination of thecentral optical zone and, in addition, precluded intra-operative orpost-operative adjustment of the patient's refractive power.

Therefore, there remains a need for a surgical technique which canachieve intra-operative correction of refractive error to eliminate theneed for eyeglasses and contact lenses by modifying the cornealcurvature which avoids delamination of the central optical zone andpermits intra-operative and post-operative adjustment of the patient'srefractive power, and which is also reversible. There further remains aneed for such a technique wherein the surgical equipment is relativelyinexpensive and only moderate skills are required.

SUMMARY OF THE INVENTION

The present invention describes a technique and set of surgicalinstruments which allow for the surgical correction of myopia andastigmatism by controlled injection of a polymeric gel or elastomer atthe corneal periphery without interfering with the central cornea andendothelium. More particularly, the surgical technique of the inventionallows for subtle modification of the corneal curvature by interlamellarinjection of a synthetic or natural polymeric gel at the cornealperiphery while sparing the optical zone. In accordance with theinventive surgical procedure, a partial depth, radial incision is madeoutside the optical zone. A corkscrew-like delaminator, for example ahelicoidal spatula, is inserted through the incision to form an annulartrack centered about the corneal apex. A modified needle is then fullyor partially inserted in the interlamellar track formed by thedelaminator and a transparent gel is manually injected while retractingthe needle, thus filling the annular channel, or the gel can be directlyinjected into the channel. By monitoring the corneal shape with anautomatic keratometer, for example, emmetropia can be achievedintra-operatively by controlling the amount of gel injected and bycorneal massage. Using a surgical keratometer mounted to an operationalmicroscope, the final corneal power is adjusted by removal of a portionof the gel.

Thus, the use of an injectable substance gives the method, in additionto technical simplicity, the possibility of adjusting the quantity ofmaterial to obtain the desired correction. It is also possible toextract or remove this material to reverse the procedure, or augment itsvolume if necessary.

Other objects, features, and characteristics of the present invention,as well as the methods of operation and functions of the relatedelements of the structure, and the combination of parts and economies ofmanufacture, will become more apparent upon consideration of thefollowing description and the appended claims with reference to theaccompanying drawings, all of which form a part of this specification,wherein like reference numerals designate corresponding parts in thevarious figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view showing the use of a caliper tolocate and mark the central cornea and incision site in accordance withthe invention;

FIG. 2 is a schematic perspective view of an ultrasonic pachymeter formeasuring corneal thickness in accordance with the procedure of theinvention;

FIG. 3 is a perspective view of a diamond knife equipped with amicrometer;

FIG. 4 is a schematic cross-sectional view of an incision formed inaccordance with the invention;

FIG. 5 is a schematic elevational view showing the incision of thecornea in accordance with the invention;

FIG. 6 is a schematic elevational view showing the insertion of a bluntspatula in accordance with the invention for separating the lamella;

FIG. 7 is a schematic elevational view of the insertion of ashoehorn-like device for facilitating insertion of a corkscrewdelaminator in accordance with the invention.

FIG. 8 is a schematic elevational view of the insertion of a corkscrewdelaminator;

FIG. 9 is a perspective view, partly in cross-section and partly brokenaway for clarity, illustrating the formation of an annular track with acorkscrew delaminator in accordance with the invention;

FIG. 10 is a schematic elevational view of the incision site followingcomplete insertion of the corkscrew delaminator;

FIG. 11 is a schematic cross-sectional view showing the injection of gelwith the needle in accordance with the invention;

FIG. 12 is a perspective view, partly in cross-section and partly brokenaway for clarity, showing the retraction of the needle while the gel isinjected;

FIG. 13a is a schematic cross-sectional view of the cornea with theneedle within the annular track;

FIG. 13b illustrates the track with gel so as to bulge the cornealposterior lamellae and flatten the central corneal optical zone;

FIG. 14 is a schematic perspective view illustrating localized cornealshear variations generated at the limbus which produces astigmatism andtheir effect on the gel injected in accordance with the invention;

FIG. 15 is a schematic top plan view of a modified procedure inaccordance with the invention;

FIG. 16 is a schematic cross-sectional view of a gel injector suitablefor use in accordance with the invention;

FIG. 17 is a plan view of a track width equalizer for use in accordancewith the invention;

FIG. 18a is a perspective view, partly in phantom, of a differentembodiment of the corkscrew delaminator in accordance with theinvention;

FIG. 18b is a cross-sectional view of the helicoidal section of thecorkscrew delaminator of FIG. 18a;

FIG. 18c is fragmentary enlarged view of one embodiment of the tip ofthe corkscrew delaminator of FIG. 18a;

FIG. 18d is a fragmentary enlarged view of another embodiment of the tipof the corkscrew delaminator of FIG. 18a;

FIG. 18e is a fragmentary enlarged view of still another embodiment ofthe tip of the corkscrew delaminator of FIG. 18a;

FIG. 19 is a schematic cross-sectional view of the annular track formedin the cornea with the delaminator shown in FIGS. 18a and 18c;

FIG. 20 is a schematic cross-sectional view of the annular track formedin the cornea with the delaminator shown in FIGS. 18a, 18d and 18e;

FIG. 21a is an elevational view of an alternative embodiment of ashoehorn-type device for use in the present invention;

FIG. 21b is a side view of the device shown in FIG. 21a;

FIG. 22a is a perspective view of a channel starting device for use inthe present invention;

FIG. 22b is a fragmentary enlarged view of the end of the device shownin FIG. 22a;

FIG. 22c is a cross-sectional view taken along lines 22c--22c of FIG.22b;

FIG. 22d is an elevational view of the device shown in FIG. 22a;

FIG. 23a is a perspective view of a marking instrument for use in thepresent invention;

FIG. 23b is a fragmentary view of an alternative embodiment of theinstrument shown in FIG. 22a; and

FIG. 24 is a perspective view of a syringe for use in the presentinvention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENT

The exact physical properties of the cornea and scleral limbal tissueshave not been determined. However, if the cornea resists stretching, itcan easily be delaminated. The large differential in modulus ofelasticity between the two orthogonal corneal planes is responsible forthe effects observed with the procedure of the invention.

The corneal lamellae are laid parallel to Bowman and Descemet layers andhave a radial elastic modulus of approximately 5×10⁶ N/m² and atransverse elastic modulus of 3×10⁴ N/m². These lamellae are weaklybounded and can be easily separated.

The scleral-limbal region forms an annulus (the corneal limbus) muchmore rigid than the cornea and act as a reference frame with respect tocorneal deformation. With the procedure of the invention, the limbusgeometry and physical characteristics remain stable (unchanged).Therefore, the procedure of the invention causes a redistribution of thenominal corneal stresses produced by the positive intraocular pressure.This redistribution causes a change in the corneal shape with aflattening of the central corneal radius of curvature and a steepeningof the site of gel injection. However, the inner and outer cornealsurface areas are kept constant. Therefore, little change occurs instress applied along the individual lamella. As the laminar network iskept intact except for the small incision site, a very minimal woundhealing effect is expected. Thus, the keratometric changes produced bythe procedure of the invention are expected to be stable in long-termfollow up.

The procedure in accordance with the invention is as follows:

First, the central cornea and the incision site are defined and markedon the eyeball 10 with the help of a standard caliper 12 as shown inFIG. 1. Specifically, the surface of the eyeball is dried with blottingpaper and marked with a compass, for example a Castroviejo Caliper #E2404 available from Storz, Inc. having blunt needles or points whichhave been previously soaked with ink from an epidermic labeler, such as#150 available from Devon, Inc. The ink soaked needles are placed on theeyeball to mark the corneal center and the incision site between about2.5 and 3.5 mm from the apex, a distance corresponding substantially tothe internal radius of the corkscrew delaminator used to form theintra-laminar canal in accordance with the invention. Additional marksmay be made at that predetermined distance from the corneal center tomark a guide for the dissector to follow during the surgical maneuver.Once the central cornea and incision site have been selected and marked,the corneal thickness is determined with a conventional ultrasonic probeand pachymeter 14 at the corneal center and at the incision site asshown schematically in FIG. 2.

An instrument for facilitating the marking of the cornea for theincision site is shown in FIG. 23a. Marking instrument 15 consists of ahandle section 15a and a guide section 15b. Guide section 15b has anopening 15c and a pair of parallel arms 15d and 15e which are connectedby a rounded section 15f. Parallel arms 15d and 15e terminate in a pairof points 15g. Instrument 15 is used by aligning the apex of roundedsection 15f with the corneal center, such that points 15g of parallelends 15d and 15e will indicate the inner diameter of the channel formedby the delaminator. In the present embodiment, the distance betweenpoints 15g is preferably 5 mm. Finally, a raised section 15h on handlesection 15a offers the surgeon a comfortable and secure grip when usinginstrument 15.

A second embodiment of instrument 15 is shown in FIG. 23b as 15'.Instrument 15' contains a central prong 15j located between points 15g.Prong 15j acts a centering device, which when positioned at the cornealcenter, locates points 15g at the proper incision sites.

A partial depth incision 20 is then performed at the incision site witha diamond knife 16 which is equipped with a micrometer (not shown)having a footplate 18 (FIG. 3). The blade length is adjusted to about86% of the corneal thickness, as measured by the pachymeter. The knifeis then used to form a radial incision to a depth D of between 75% andabout 85% and most preferably between about 75% and about 80% of thecorneal thickness T. To obtain a flat-bottomed incision with verticalwalls, the diamond blade can be reversed and moved radially with respectto the center of the cornea (FIG. 4). The foregoing two step procedurewith the diamond blade can be avoided by the use of a flat-edged blade.The insertion of the diamond knife 16 to the predetermined 80%±5% depthof the cornea 22 is illustrated in particular in FIG. 5. The incision isperformed to a length L of about 1.0 mm or less and most preferablyabout 0.4 mm which is preferably between 0 to 0.5 mm less than the widthof the delaminator to be used. The incision is preferably made as smallas possible so as to minimize wound healing time following theprocedure.

Once the incision has been formed, a spatula 24 such as, for example, aCastroviejo cyclodialisis spatula #E 0292 available from Storz, Inc.having dimensions identical to that of the helical spatula, for exampleabout 1 mm or less in width and 200 micrometers in thickness and havingan end which is slightly modified by being polished to a point, isinserted through the incision to separate the lamella in the plane ofthe base of the incision (FIG. 6). The particular width of the spatulaused of course depends upon the length of the incision. Alternatively,once the incision has been made to the desired depth in the cornea, aninstrument is inserted into the incision to locate the proper planealong which to separate the lamella and form the intralamellar canal inaccordance with the invention. A channel starting instrument 25 (FIGS.22a-d) consists of a handle 25a, a central section 25b, and end section25c. Central section 25b is preferably coaxial with the central axis ofhandle section 25a, and is formed from a flat wire. As can be seen inFIG. 22d, end section 25c, which is shown as curved but may be linear,is attached to central section 25b at an acute angle α to the centralaxis through sections 25a and 25b, which angle is preferably between 40°and 45°. End section 25c consists of a curved or arcuate portion 25d anda smaller portion 25e which is also curved. Preferably, section 25c isconstructed having the same radius of curvature of the helical spatulato be used for the procedure. Portion 25d is formed out of a flat wire,while portion 25e consists of a semicircular section of curved wire, ascan be most clearly seen in FIG. 22c. Instrument 25 is used by insertingend section 25c into incision 20 until section 25c contacts the bottomof the incision. Handle section 25a is then rotated in a manner suchthat the lamella is separated along an arcuate path by curved portion25e of end section 25c. Handle section 25a contains a knurled portion25f to assist the user in gripping the instrument.

Following the initial separation of lamella with the blunt spatula 24and starting the channel with instrument 25, a shoehorn-type device 26is inserted through the incision and laterally between the lamella asshown in FIG. 7. The shoehorn-type device 26 can be made of plastic orstainless steel or any material which is more rigid than the radialelastic modulus of the cornea, which measures approximately 5×10⁶ N/m².The thickness of device 26 may approach 300 microns, with the preferredrange being between approximately 50 to approximately 100 microns.

An alternative embodiment of shoehorn-type device 26 is more clearlyshown in FIGS. 21a and 21b. Referring now to FIGS. 21a and 21b, device26' is a planar member having an upper horizontal section 26a' and adownwardly depending extension 26b'. The upper end 26c' of extension26b', which is narrower than upper section 26a', depends from thecentral region of section 26a' at an approximate angle of 90°, andextension 26b' may be either slightly curved or straight as it continuesaway from upper section 26a' until it reaches its lower end 26d', whichend is rounded for ease of insertion into the incision. The length ofextension 26b' may range between 1 and 6 mm, while its width should beless than or equal to the width of the delaminator.

Ideally, the radius of curvature of extension 26b' should match theradius of curvature of the helical delaminator.

Extension 26b' of device 26' is inserted into the incision until uppersection 26a' contacts the upper surface of cornea 22. The curvature ofextension 26b' of device 26' facilitates the insertion of spatula 28 tothe proper plane for delamination which has been selected and started byinstrument 25 and guides spatula 28 as it begins to form annular chamber30. The design of shoehorn-type device 26' also provides for easierinsertion and extraction of device 26' from the incision site.

The shoehorn-type instrument is utilized for facilitating insertion of acorkscrew delaminator or helicoidal spatula 28, for example a custommade Archimedes-screw dissector which is inserted behind or undershoehorn device 26, as shown in FIG. 8. The flat corkscrew delaminatoris used to carve a circular canal between the two corneal lamellae inwhich a gel such as a silicon gel is subsequently injected. Theillustrated corkscrew delaminator consists of a flat wire between 0.25and 4.5 mm, preferably about 1 mm in width as in the preferredembodiment, again depending upon incision length and 0.1 mm inthickness, and is curved to about 380°, that is superimposed by 20°. Thespatula's edges are blunt or rounded as is its end. The inner diameterof spatula 28 may fall within the range of 2.0 to 10.5 mm, with thepreferred embodiment measuring approximately 5 mm.

As shown in FIG. 9, with the corkscrew delaminator, an annular track ismade through the cornea at the preselected plane. A full 360° twistingmotion of the helicoidal spatula 28 delaminates the cornea completely atthe radial location of the incision, circumferentially of the centralcorneal zone. However, the central and paralimbal zones of the corneaare not delaminated as the helicoidal spatula 28 limits the delaminationto an annular path at the radial locus of the incision. As shown in FIG.10, the annular delamination results in the formation of an annularchamber or canal 30 opening on either side of the initial incision 20.Following the annular delamination, the helicoidal spatula 28 is removedby rotating the same with a reverse 360° twisting motion. When spatula28 is removed, it may be necessary to ensure that the canal 30 openingson either side of the initial incision 20 are uniform to allow for theproper flow of gel through canal 30. A track width equalizer 31 (FIG.17) is used for this purpose. Equalizer 31 contains a handle portion31a, a curved portion 31b, and a rounded end portion 31c. End portion31c, which typically measures 0.5 mm in diameter, is inserted throughincision 20 into each canal 30 opening, thus insuring that the injectedgel will pass through canal 30. Equalizer 31 is also used to remove thegel if necessary.

A small corkscrew-like cannula 32, in the range of 19 to 30 gauge insize, preferably 30 gauge in the present embodiment, is then insertedinto the annular channel 30. A syringe, for example filled with abiocompatible gel, is attached to the corkscrew cannula 32 followinginsertion or prior to insertion into the annular channel 30. Examples ofsuitable biopolymeric materials for the gel are known biocompatiblehydrogels (e.g. acrylic hydrogels, polyethylene oxides), silicone-basedcross-linked elastomers, and other biopolymers (e.g. cross-linkedhyaluronic acid). One gel which has been found to be suitable for use inthe present invention is a crosslinked polyethylene oxide (PEO) gelwhich is prepared by dissolving a sample of PEO in a Balanced SaltSolution (BSS), placing the solution in a sealed canister, removing anyfree oxygen from the interior of the canister, replacing the oxygen withan inert gas such as argon, irradiating the canister to crosslink andsterilize the PEO, and loading the sterilized PEO into a sterilesyringe. This method is more completely described in co-pendingapplication Ser. No. 08/299,583, which was filed on the same dateherewith and is assigned commonly herewith. The disclosure of thepending application is incorporated herein by reference. This gel has amodulus of elasticity of approximately 1.7×10³ n/m² and an index ofrefraction of 1.334. Once the corkscrew cannula is inserted, injectionis started (FIG. 11).

It is also possible to inject gel 34 directly into canal 30 by using anautomatic injector 40 (FIG. 16). Injector 40 consists of a poweredinjector unit 40a and a gel cartridge unit 40b. Unit 40a can becontrolled by a manual switch on the unit, or by a foot pedal switch.Cartridge 40b is a disposable sealed unit to prevent contamination, andfits onto unit 40a for easy, sterile operation. Injector 40 provides aconsistent force to inject gel 34 into canal 30.

Another alternative for injecting gel 34 into canal 30 is shown in FIG.24. A syringe 42 having a gel storing compartment 42a, a plunger 42bcaptively held with compartment 42a, and a cannula 42c coupled to theend of compartment 42a may be used to inject gel 34. Cannula 42c has acurved end 42d which is helicoidal or spiral shaped such that it can beeasily inserted through incision 20 and into canal 30, thus insuringthat gel 34 will completely fill canal 30 as syringe 42 is operated. Thecurvature of end 42d of cannula 42c is preferably matched to thecurvature of helicoidal spatula 28.

A small amount of gel escapes from the corneal incision due to overpressurization (FIG. 11). Furthermore, subsequent to needle removal, anexternal massage is performed in order to evenly distribute the gelinside the canal. The remaining gel that appears at the incision isgrabbed with forceps and cut, for example with scissors. Once the 30gauge needle has been removed, gel fills the track creating a bulging ofthe corneal posterior lamellae and a flattening of the central cornealoptical zone. FIG. 13a is a corneal cross-section illustrating thedisplacement of the corneal lamella when the needle 32 is disposed withan annular track 30. Once the needle has been retracted and gel fillsthe annular canal 30, a bulging of the cornea posterior lamella and aflattening of the central corneal optical zone occurs (FIG. 13b). Up to13 diopters of flattening have been obtained in cadaver eyes with thetechnique of the invention. By removing a portion of the gel from thechannel, the amount of corneal flattening can be reduced untilemmetropization has been achieved. Intraoperative keratometry issuggested for determination of optimal corneal radius of curvaturealthough other techniques could be employed. The amount of correctionobtainable is a function of the inner diameter and wire width of thedelaminator, in addition to the amount of gel used.

Referring to FIG. 14, astigmatism is thought to be produced by localizedcorneal shear variations generated at the limbus. With the process ofthe invention, a reduction of existing astigmatism was observedexperimentally. This phenomenon can be explained by a localizedvariation in gel distribution along the annular channel as shown.Indeed, because the pressure of the gel is constant, it equilibriatesthe radial stresses along the corneal meridian.

Astigmatism may also be corrected in accordance with the presentinvention by using a modified procedure as illustrated schematically inFIG. 15. In accordance with this modified procedure, a pair of arcuatechannels 50 of approximately 90° in arc length and centered about thecorneal center 52 are made by a stromal delaminator (not shown) which isa shorter version of the helicoidal delaminator discussed in detailabove. A gel, as discussed above, is then injected into each of thearcuate channels 50 under keratometric control. The magnitude of theastigmatic optical correction in diopters is a function of the amount ofgel injected into each of the arcuate channels 50, the size, that isdiameter, width and angle of the arcuate channels, and the position ofthe two arcuate channels with respect to the patient's cornealastigmatic (flattest) axis 54.

As noted above, minimizing the length of the incision, in accordancewith the invention, reduces wound healing time. To further reduce woundhealing time, following gel injection and the removal of any excess gel,the corneal incision can be instantly closed-shut by applying a verysmall amount of collagen gel to the upper lips of the wound and crosslinking it with ultraviolet radiation. Such sealing of the incisioneliminates post operative patching of the eye and thus allows thepatient to walk away from surgery without impediment. Ultraviolet crosslinkable collagen gels are fabricated by several manufacturers and asuitable ultraviolet cross linkable collagen gel among those availablecould be readily ascertained.

Another advantage of the present invention over current surgicaltechniques is reversibility. Should it become necessary to readjust thecurvature of the cornea at some later time, such as a year later, alinear incision is made above the channel to a depth which intersectsthe channel. The gel can then be removed by massaging the cornea oradditional gel may be added as previously described until the desiredcorneal shape is obtained and then the incision is closed using theabove described technique.

FIGS. 18a-18e show alternative embodiments of a helicoidal delaminatoror spatula for use in the present invention. Spatula 44 consists of ahelicoidal section 44a, a planar support section 44b, and a handlesection 44c which is fixed to support section 44b by welding or asimilar attachment means. Handle 44c allows helicoidal spatula 44 to bemore easily manipulated during surgery. The design of handle 44c,consisting of an annular cylindrical ring, is important, as it allowsthe surgeon an unobstructed view of the corneal surface as he is usingthe device. Handle 44c of spatula 44 is provided with a pair ofindicating marks 60 and 62 on its upper surface. Marks 60 and 62 may beused to indicate relative position of section 44a of spatula 44 when itis within channel 30 that has been formed in cornea 22, as section 44ais no longer visible. Mark 60 is used to indicate the position of theend of the nose portion of helicoidal section 44a so that the surgeoncan determine when he has completed the formation of channel 30. Mark 62indicates where the overlapped portion of helicoidal section 44a begins.Marks 60 and 62 facilitate the use of spatula 44 during the procedure byeliminating uncertainty with respect to its position.

FIG. 18b shows the cross-section of the helicoidal section 44a ofspatula 44. It can be seen that section 44a imitates the radius ofcurvature of the cornea, which is approximately 7.8 millimeters, suchthat channel 30 closely parallels the surface curvature of the cornea.

In the embodiment shown in FIG. 18c, spatula 44 contains a nose portion44d which is tapered along the top edge toward its end. When spatula 44is used in the corneal surgical procedure described in the presentinvention, nose portion 44d creates a lameliar flap within the trackformed by spatula 44 within the cornea. As can be seen in FIG. 19,lameliar flap 22a within cornea 22 aids in sealing channel 30 fromincision 20, thus preventing gel from freely escaping from incision 20.Thus, this modification to spatula 44 eliminates the need for adhesivesor the like to bond the incision in the cornea. Nose portion 44d tendsto keep channel 30 in the lower portion of the cornea.

FIG. 18d shows an alternative embodiment of the end of spatula 44. Noseportion 44e is tapered along the bottom edge of section 44a toward itsend. When spatula 44 is used in the corneal surgical procedure describedin the present invention, nose portion 44e creates a channel as shown inFIG. 20. This channel 30 intersects incision 20 directly. Nose portion44e tends to keep channel 30 in the upper portion of cornea 20.

FIG. 18e shows another alternative design for the end of spatula 44.Nose portion 44f is v-shaped at the end of spatula 44, and also createsa channel as shown in FIG. 20. Nose portion 44f tends to keep channel 30in the middle portion of cornea 20.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

Indeed, while the presently preferred incision location and depth whichhave been specified have exemplary dimensions of instruments used inconnection with the inventive procedure, it is to be appreciated thatthe gel viscosity, volume and disposition within the surgical annulartrack as well as the diameter of the track, width, depth and locationare all parameters in the refractive change obtained in accordance withthe invention.

What is claimed is:
 1. A guiding device for facilitating the insertionof a delaminating device into an incision in the cornea for separatingthe lamellae of the cornea during a procedure for altering the radius ofcurvature of the cornea of an eye, said device comprising:a firstsection consisting of a flat planar surface of uniform thickness forinsertion into an incision in a cornea for guiding the end of adelaminating device between the lamellae of the cornea at a selecteddepth, and a second section, coupled to said guide section, forcontacting the surface of the cornea to limit the depth of travel ofsaid first section into the incision, wherein said first and secondsections are coplanar, and wherein said first section extendscurvillinearly from said second section.
 2. The device as in claim 1,having a thickness of less than 300 microns.
 3. The device as in claim2, wherein its thickness measures between approximately 80 microns andapproximately 100 microns.
 4. The device as in claim 1, whereby saiddevice is composed of stainless steel.
 5. The device as in claim 1,having a rigidity greater than approximately 5×10⁶ newtons/meter². 6.The device as in claim 1, whereby said device is composed of plastic. 7.The device as in claim 1, wherein said first and second sections aresubstantially perpendicular to each other.
 8. The device as in claim 1,wherein the length of said first section ranges between 1 millimeter and6 millimeters.
 9. The device as in claim 1, whereby said second sectioncontains portions for contacting the surface of cornea extending furtherthan both outer edges of said first section.
 10. A guide forfacilitating the insertion of a curved delaminating device into anincision in the cornea for forming an annular channel between lamellaein the cornea at a desired depth spaced radially from the central regionof the cornea during a procedure for altering the radius of curvature ofthe cornea of an eye, said guide comprising:a first section consistingof a flat planar surface of uniform thickness for insertion into anincision in the cornea for guiding a curved delaminating device betweenlamellae at a desired depth within the incision; and a second sectionconsisting of a flat planar surface of the same uniform thickness assaid first section, coupled to and co-planar with said first section,for contacting the surface of the cornea to limit the depth ofpenetration of said first section into the incision in the cornea,wherein said first section extends curvillinearly from said secondsection at the same radius of curvature as the curved delaminatingdevice.
 11. The guide as in claim 10, having a uniform thickness of lessthan 300 microns.
 12. The guide in claim 11, wherein its thicknessmeasures between approximately 80 microns and 100 microns.
 13. The guideas in claim 10, wherein the width of said first section is less than thethickness of the delaminating device.
 14. The guide as in claim 10,having a rigidity greater than 5×10⁶ newtons/meter².
 15. The guide as inclaim 10, wherein said device is composed of plastic.